Reassurance (Sans x Frisk x Gaster)
by GoldGuardian2418
Summary: Frisk is still unsure about Gaster, but he and Sans are willing to show her that she doesn't have to be afraid of the tall skeleton. Tickle story! Fluff and cuteness inside! :)


**This idea came to me one day and I was like, yeah, why not? :)**

 **Now, this isn't a romance story. Sans is a loving dad/uncle to Frisk and Gaster is Sans' older brother in this story, so he's also Frisk's uncle.**

 **Undertale belongs to Toby Fox. I own nothing.**

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 **Reassurance (Sans x Frisk x Gaster)**

Frisk wrapped the blanket around herself as she tried to fall asleep, but she had a lot on her mind. One particular person actually.

Frisk had decided to go exploring and had found the strange door again and had found the strange skeleton with holes in his hands waiting for her. She had backed away, but he followed her out the door calmly. Sans had been nearby when he saw them and had slowly walked up to them. The strange skeleton looked at Sans and kneeled down, speaking Sans' name.

The shorter skeleton had practically tackled his older brother in a hug and then turned and hugged Frisk. "You saved him too, kiddo," Sans had said. "I was hoping when the barrier broke that he'd come back."

She had looked at him. "Sans, who is he?" She had asked.

"Mine and Papyrus' older brother, Gaster."

Frisk remembered when she first encountered Gaster, she had been scared and that fear came back. The taller skeleton seemed to sense that and suggested they head for home.

Papyrus was overjoyed too, but Frisk slipped away to her room, still scared of Gaster, even remembering the River Person once saying to beware the man that spoke with his hands. She had seen Gaster use his hands to speak along with using his voice.

Sighing, she got up and walked to Sans' room, hoping he'd agree to a sleepover. She gently knocked on the door. "Sans?" She called out softly.

Not hearing him, she entered the room, finding the shorter skeleton laying back on his bed with his eyes closed. The door to the bedroom suddenly shut and she jumped sharply, bumping into a tall black being. Seeing him kneel down towards her, Frisk whimpered and her legs buckled, making her fall to the floor and curl up, shivering fearfully.

Sans woke up when he heard Frisk whimper and saw Gaster kneeling down, lifting the young girl up from the floor. Frisk's shaking grew worse and she whimpered again.

Wondering why the young girl was afraid of him, Gaster brought her over to Sans, who accepted her from his older brother. "Hey, Frisk," he said, feeling her cling to him and she stopped shaking. "Why are you so scared of my brother?"

Frisk didn't answer as she clung to him and he sat up more, holding her and rubbing her back. "Shh, it's okay. Gaster won't hurt you," he said reassuringly.

Gaster sighed. "Sans, this isn't the first time she met me," he said. "She met me before the barrier was broken and my appearance scared her."

Understanding dawned on Sans' face as he continued rubbing Frisk's back, but then he looked confused. "But, you're a skeleton like me and Paps, bro," he said. "If she's not scared of two skeletons, why would she suddenly be afraid of you?"

Sans suddenly went still, remembering Frisk had told him about the River Person's sayings and was confused at one saying.

" _Beware the man who speaks with his hands."_

The shorter skeleton looked down at Frisk. "Frisk? Are you scared of Gaster because he's the one the River Person was talking about?" He asked.

The young girl looked up at him and nodded. Sighing, Sans gestured for Gaster to sit on the bed with them as the shorter skeleton lifted the young girl up and sat her down beside him gently. She noticed Gaster was sitting beside them too and scooted closer to Sans. "Kiddo," Sans began. "Gaster can speak with his hands and like how Papyrus and I can, but because he can, a lot of others didn't understand and so grew afraid of Gaster, telling other monster kids that the man that spoke with his hands was dangerous. It took some help from Undyne to straighten some of the rumor out, but many still say that, even after Gaster disappeared for so long until now."

He then gently squeezed Frisk's shoulder. "Frisk, do you trust me?" He asked.

She nodded. "So, do you believe me when I say Gaster won't hurt you?" He asked.

Frisk looked unsure and Sans decided to try and smooth the situation over a bit. "We were talking about you earlier and Gaster said when he saw you, he hoped that you free us from the Underground. He believed in you the whole time, just like Papyrus and me."

The young girl looked up at him and he smiled reassuringly. "You know, you speak with your hands sometimes, Frisk," he pointed out gently. "Remember when you wouldn't use your voice until I managed to make you laugh not long after you met Papyrus and I?"

She nodded. "Well, why would we be scared of you when you showed us humans were good and we showed you that monsters could be good too?" He asked. "How do you think Papyrus and I knew what you were signing when we met you?"

Frisk looked over at Gaster, who smiled gently at her and nodded. "Yes," he said. "I taught my younger brothers both sign language and Wingdings."

Frisk cocked her head curiously at the last word and Gaster chuckled. "Wingdings is similar to sign language," he explained and wrote a couple words in Wingdings and wrote their translations underneath on a piece of paper and showed her. The young girl studied it curiously and Sans chuckled.

"Neat, huh?" He asked.

She nodded, giving the paper back to Gaster. "Yeah, it's really neat," she answered.

Gaster suddenly grinned and winked at Sans. "There's something else I can do with my hands too," he said.

Sans quickly caught on. "Great idea, bro," he said, gently wrapping his arms around Frisk and holding her with her back to his chest. "This little kiddo is very ticklish."

Frisk tried to squirm away, squeaking when she saw Gaster gently remove her socks and used one arm to gently pin her bare feet in his lap. A wiggling finger touched the sole of Frisk's right foot and she instantly began giggling. "My, my. Listen to that giggle," Gaster said with a smile. "Remember Papyrus would be in a fit of giggles and I hadn't even begun tickling his feet?"

Sans nodded. "He was a wiggle worm too. Still is," he said as he tightened his hold on Frisk a little, just enough to where she was comfortably secure, but had some wiggle room to just squirm, but not be able to escape.

Gaster chuckled as he secured Frisk's bare feet gently under one arm and thanks to his long arms, was able to use both hands to tickle the child's feet.

Frisk's giggles grew louder as she tried to pull her legs free, but then squealed feeling Gaster tickling right under her toes with one finger while the rest of his fingers continued tickling her feet before he turned slightly and tickled the backs of Frisk's knees, which made her giggle louder and she again squealed when the tall skeleton began tickling her calves.

Gaster then showed some mercy and let Frisk catch her breath. He then gently poked her sides and ribs and tickled her underarms lightly and smiled when she giggled and when he moved his hands towards her stomach, she tried to curl up, but could only bring her legs up to try and shield her stomach. "So you have a very sensitive stomach, hmm?" Gaster asked teasingly.

"Oh, yeah," said Sans, leaning close to Frisk's right ear. "And she loves it when we tickle her stomach," he said right in her ear.

Frisk giggled at that and saw Gaster smile at her before letting her have another breather. He then smiled wider. "Sans, do you remember the story I made for you and Papyrus?"

Grinning, Sans nodded. "Frisk would love that," he said, grinning again as she looked up at him.

"What story?" She asked.

Gaster smiled. "Sounds like she'd like to hear it," he said.

Sans nodded. "She's one of the family, so she definitely needs to hear the special story," he said.

Frisk felt Sans' arms loosen on her a little, but she still wanted to snuggle and so settled down as Gaster smiled at her and gently ruffled her hair.

" _Little Baby Bones creep softly,_

 _Eyes wide and brightly looking,_

 _Watching for the tickle monster,_

 _But he sees them and follows."_

Frisk squirmed, grinning as Gaster playfully wiggled his fingers at her, and she got the idea this was a tickle story. Focusing on Gaster, she saw him smile again before he continued the story.

" _Clutching a small blanket tight,_

 _Little eyes looking, watchful,_

 _Suddenly, they softly trip,_

 _And eager fingers wiggle into little ticklish feet."_

The tall skeleton tickled Frisk's feet again and she giggled before pulling them away from his hands and he let her. Sans smiled as he held onto the young girl as his older brother continued.

" _Baby Bones run quickly,_

 _Dropping the blanket that long fingers pick up,_

 _A form emerges with a big smile,_

 _Ears hoping to hear a child's sweet laugh,_

 _He follows softly after the little one."_

Frisk felt Sans shift so that he could whisper in her ear. "Pretend to look around now," he whispered to her.

Sensing this was part of the story, Frisk did as she was told while hearing the taller skeleton speak again.

" _Little Baby Bones glance around,_

 _But sees nothing,_

 _Although they hear a noise,_

 _And see long fingers coming towards them."_

The young girl tried not to giggle as she began picturing the story and seeing Gaster wiggle his fingers at her again in a playful manner and she squirmed again, holding onto Sans.

" _Seeing the little one move away,_

 _He smiles and follows still,_

 _Knowing soon the child will be laughing,_

 _As on their tickle spots his fingers will dance._

" _Baby Bones hear words indistinguishable,_

 _Yet they are gentle to hear,_

 _Pausing for a brief moment,_

 _Long fingers gently poke their sides and ribs."_

Gaster now did what he spoke, tickling Frisk's sides and ribs, making her giggle louder and more.

" _Moving away again, Baby Bones is thirsty,_

 _And goes to the kitchen,_

 _Turning on the light to expose the tickle monster,_

 _But finds the tickle monster there with a friend."_

Sans chuckled, giving Frisk a wink as she realized his role in the story and she smiled. "Doing okay?" He asked in a whisper.

She nodded. "I can picture it in my head like how when you tell me stories," she whispered back to him.

She then looked at Gaster, who had paused in the story and his grin told her they had just come to the best part before he began speaking again.

" _Trapped, the child looks up in fear,_

 _Only to feel gentle fingers tickle their sides,_

 _Before tickling fingers tickle the child's stomach."_

Giggles and laughs poured out of Frisk's mouth as she felt the tall skeleton's long fingers tickle her stomach once more and she decided she was liking the story too much to ask Gaster to stop tickling her, something he seemed to notice and smiled after another pause.

" _The tickle monster smiles again,_

 _Hearing such a sweet sound,_

 _Gently tickling little Baby Bones,_

 _Until seeing little eyes look sleepy._

" _Baby Bones feels their blanket surround them,_

 _As arms as gentle as the tickling fingers,_

 _Hold them while letting them get a drink of water,_

 _And then carrying them back to their room."_

" _Before tucking them in,_

 _The tickle monster has one more trick,_

 _Blowing raspberries into Baby Bones' tummy,_

 _And tickling ticklish toes gently."_

Gaster now lifted Frisk's shirt up to the bottom of her ribcage and took a deep breath before blowing a raspberry into the small stomach. Frisk squealed as Gaster didn't stop blowing raspberries into her stomach for a while. He even tickled her toes again as he kept up the raspberries into the young girl's stomach for a few minutes before seeing she had enough and he chuckled.

" _Last, but not least, as the tickles end,_

 _A sleepy little head nods a little,_

 _Baby Bones hold out little arms,_

 _Which the tickle monster sees and smiles."_

Smiling, Frisk held out her arms to Gaster, who smiled at her and picked her up as he finished the story.

" _Again, gentle arms surround and hold,_

 _As soft words are said in little ears,_

 _Little eyes on an angel's face close,_

 _Knowing they have found a true friend."_

As Gaster finished the story, Frisk snuggled into his hug, yawning a little as he returned the hug. "I like that story," she said honestly.

Sans chuckled. "Gaster came up with it for when Papyrus couldn't sleep and he'd even use the story to help me sleep too," he explained.

Frisk yawned. "It made me sleepy too," she admitted. "I couldn't fall asleep earlier."

"Neither could we, little one," Gaster admitted.

"Sounds like a sleepover is due," Sans said as he watched his older brother pull the covers back a bit and let the shorter skeleton and the young girl slip under the covers before Gaster slid under the covers himself, tucking the other two in.

Frisk suddenly turned toward him and hugged him again. "Love you, Uncle Gaster," she said.

He chuckled. "I love you too, my little niece," he said, returning the hug, placing an affectionate kiss on her forehead.

Sans smiled and then saw Frisk turn to him and hug him too. "Love you, Dunkle Sans," she said softly.

No matter how many times he heard that, Sans loved hearing that. "I love you too, baby bones," he said with a smile, kissing her forehead affectionately as the three of them cuddled together and fell asleep.

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 **The tickle story that Gaster tells Frisk is one I came up with.**

 **Please leave a review, but no flames!**

 **GoldGuardian2418**


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